NL8301437A - DEVICE FOR MANUFACTURING PHOTOVOLTAIC DEVICES. - Google Patents

Description

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Subject: Device for the manufacture of photovoltaic devices.

The invention relates to a device for the continuous production of photovoltaic devices on a strip of magnetic substrate material by depositing successive semiconductor layers consisting of amorphous silicon alloys in each of at least two adjacent deposition chambers. each amorphous layer is dependent upon the particular reactant gas constituents supplied to each of the deposition chambers. The components fed into the first deposition chamber are carefully controlled and isolated from the components fed into the adjacent deposition chamber. More specifically, the deposition chambers are connected by a relatively narrow gas port channel (1) through which the strip of substrate material passes, and (2) intended to isolate the reactant gas components fed to the first deposition chamber from the reactant gas components supplied to the adjacent deposition chamber. determined that, despite the relatively small dimensions of the gas port channel, dopant gas components supplied to the second deposition chamber backflush or diffuse into the adjacent first deposition chamber, thereby contaminating the layer deposited in this first deposition chamber. The invention is to reduce the dimensions of the channel in the gas port which serves to correspondingly reduce backwashing or diffusion of dopant gas components thereby reducing contamination of the layer deposited in the first deposition chamber.

Recently, great efforts have been made to develop processes for depositing amorphous semiconductor alloys, each of which may comprise relatively large areas, and which can be doped to form p-type and n-type materials for the manufacture of devices of the pin type, which are substantially equivalent to those made by their crystalline counterparts. For many years this work with amorphous silicon or germanium films has been practically unproductive due to the presence therein of micro-cavities and loose bonds leading to a high density of localized states in the energy jump. Initially, the reduction of the localized states occurred through a glow discharge 8301437

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Precipitation of amorphous silicon films in which silane (SiH2) gas was passed through a reaction tube in which the gas is decomposed by a radio frequency. 8r .f.) Glow discharge and on ·. a substrate. is precipitated at a substrate temperature of about 500-600 ° K (22T-327 ° C).

5. It on. This manner of depositing on the substrate is an intrinsically amorphous material consisting of silicon and hydrogen. In order to obtain a doped amorphous material, phosphine gas (P1) is used to conduct. The n-type, over diborane (B ^ Hg) gas for a p-type conduction is pre-mixed with the silane gas and passed through the glow discharge reaction tube under the same operating conditions. The material so precipitated is believed to include substituent phosphorus or boron doped materials and has been found to be extrinsic or of the n or p conductivity type. The hydrogen in the silane was found to combine at an optimum temperature with a large number of the loose bonds of the silicon during the glow burst, significantly reducing the density of localized states in the energy jump. amorphous material approached the corresponding crystalline material more closely.

It is now possible to prepare vastly improved amorphous silicon alloys 20 which have significantly reduced concentrations of localized states in their energy jump, while having high quality electronic properties by glow discharge. This method is fully described in U.S. Patent 4,226,898; and by precipitation from the vapor phase, as fully described in U.S. Patent 4,217,374. As disclosed in these patents, fluorine added to the amorphous silicon semiconductor serves to significantly reduce the density of the localized states therein and simplifies the addition of other alloy materials such as germanium.

30. Activated fluorine readily diffuses and bonds with amorphous silicon in a matrix body, significantly reducing the density of the localized defect states therein. This is because the small dimensions of the fluorine atoms allow them to be easily introduced into an amorphous silicon matrix. The fluorine bonds with the loose bonds of the silicon form a partially ionic, stable bond with flexible bonds. angles leading to a more stable and more effective compensation or modification, then. can be obtained by hydrogen or other condensing or modifying agents previously used. Fluorine is considered to be a more effective compensation or modification element than hydrogen when used alone or with hydrogen because of its particularly small size, high reactivity, chemical bonding specificity, and in that the material has the greatest electro-negativity.

The compensation can be obtained with fluorine, alone or in combination with hydrogen, by adding such an element. or elements in very small quantities (for example, fractions of one atomic percent). However, the amounts of fluorine and hydrogen which are preferably used are much greater than these small percentages, allowing the elements to form a silicon-hydrogen-fluorine alloy. Therefore, alloy amounts of fluorine and hydrogen can be used, for example, in a range of 0.1-5 percent or more. The alloy formed in this manner has a lower density of defect states in the energy jump than can be obtained by neutralizing only loose bonds and similar defect states. More specifically, it has been found that the use of greater amounts of fluorine provides a new structural configuration of an amorphous silicon-containing material and simplifies the addition of other alloy materials, such as germanium. Fluorine, in addition to having the above properties, is an organizer of local structure in the silicon-containing alloy via inductive and ionic effects. Fluorine also affects hydrogen bonding by decreasing the density of the defect states, which are normally contributed by hydrogen. The ionic function that fluorine performs in such an alloy is an important factor in terms of the closest nearest-30 relationships.

The concept of using multiple cells to improve the efficiency of a photovoltaic device has been discussed at least as early as 1955 by E.D. Jackson in U.S. Pat. No. 2,991-998. The multiple cells described therein used crystalline semiconductor devices having p-n junction. In essence, the concept is aimed at using devices with different energy jumps in order to be more effective 8301437

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V ζ - k - 'different.parts y an ·. collecting the spectrum, and the open-circuit voltage (Voc). The tandem flour device has two or more cells, the light of which is directed in series through each cell, with a material of high energy jump followed by. a material 5 with less energy jump for absorbing the light transmitted through the first cell or layer. By substantially matching the generated current from each cell, the total open circuit voltage is increased without the short-circuit current is practically reduced.

There have been many publications on crystalline, stacked cells after the aforementioned U.S. Patent, and more recently, a number of articles have been published dealing with Si-H materials in stacked cells. Thus, Marfaing has proposed in stacked cells using silorinated amorphous 15 · Si-Ge alloys, but he does not report their feasibility.

. (Y. Marfaing, Proc. 2nd European Gonnmmities Photovoltaic Solar Energy Conf.,. Berlin, West Germany, pp. 28j, (1979)}.

Hamakawa et al. Prefer the use of Si-i. reported a configuration, which will be defined here as a cascade type multiple cell. The cascade cell is hereinafter referred to as a multiple cell without a separating or insulating layer in between. Each of the cells was made from a Si-H material with the same energy jump in a p-i-n junction configuration. Attempts have been made to adjust the short-circuit current (J) by

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Increase the thickness of the cells in the serial light path. As expected, the total Yoc. from. the device and was proportional to the number of cells.

A recent report on increasing the cell efficiency of multiple junction solar cells (stacked solar cells) consisting of amorphous silicon precipitated from silane as described above states that "(g) ermanium appears to be a harmful impurity at Si: H, the J of which is exponentially

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low with increasing Ge ... '1. From their work, as well as from the work of Carlson, Marfaing and Hamakawa, they have concluded that alloys 35 of amorphous silicon, germanium and hydrogen have exhibited poor photovoltaic properties1 and that. Therefore, new photovoltaic film cell materials have to be found that have a spectral response at about 1 micron for efficient stacked cell combination 8301437-5-

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. Nations with an Si: H "(J-J. Anak, B. Faughnan, V. Korsun, and JP Pellican, presented at the 14th IEEE Photovoltaic Specialist Conference, San Diego, California, J-10. January 1900) -

Due to the beneficial properties obtained by introducing fluorine, amorphous alloys used to make cascade type multicellular now include fluorine to reduce the density of localized states without affecting the electronic properties of the material are adversely affected. Furthermore, an energy jump adjusting element (s), such as germanium and carbon, can be activated and added according to the vapor deposition method, splashing or glow discharge processes. The energy jump is adjusted, as required for certain device applications, by the required amounts of one or more of them. the adjustment elements in the down-15. introducing beaten alloy cells into at least their photocurrent generating region. Since the energy jump adjusting element (s) is introduced into the cells without causing harmful conditions, due to the influence of fluorine, the cell alloy retains good electronic properties and good photoconductivity when the adjusting element (s) is added to choose the wavelength characteristics of the device for a given photoresponse application. By adding hydrogen, either with fluorine or after precipitation, the fluorine-compensated or modified alloy can be further improved. Hydrogen uptake after precipitation is beneficial when it is desired to take advantage of the higher precipitation substrate temperatures made possible by fluorine. -

It is clear that it is of commercial interest to be able to mass-produce photovoltaic devices. In contrast to crystalline silicon, which is limited to "batch" treatment for the manufacture of solar cells, amorphous silicon alloys can be deposited in multiple layers over large area substrates to form solar cells in a continuous treatment system with large volume. Continuous treatment systems of this type are described, for example, in U.S. Patent Applications Serial Ho. 151.301, 2W-.386, 2 ^ 0. ^ 93, 306.1½ and 359,825. As described in these patent applications, a substrate can be continuously passed through a series of deposition chambers, each chamber being assigned to the deposition of a particular material. When manufacturing a solar cell with one. configuration of the pin type, the first chamber for depositing an amorphous silicon alloy of the p type, the second chamber for depositing an intrinsic, amorphous silicon alloy ring and the third chamber for depositing an n-type amorphous silicon alloy. Since any precipitated alloy, and more particularly the intrinsic alloy, must be of high purity, the precipitation indication in the intrinsic deposition chamber is isolated. view of the dopant components in the other chambers to prevent diffusion of the dopant components to the intrinsic chamber. In the aforementioned patent applications, in which the systems mainly concern the manufacture of photovoltaic cells, the isolation between the chambers takes place either by using gas -15 ports, which carry an inert gas around the substrate when the substrate passes through gates, or through gas tracks, which create a unidirectional flow of the reaction gas mixture which is fed into the dopant deposition chambers in the intrinsic deposition chamber. The improved magnetic gas port according to the invention results in a reduced 20. channel between the chambers, leading to a significant reduction of (1) .. impurities, which diffuse from the dopant deposition chambers or flow back to the intrinsic deposition chamber, and (2) the deformation of the substrate material, thereby reducing scratching of the substrate material and contributes to the manufacture of more effective photovoltaic devices. It is pointed out that other chambers may be connected to the chambers for depositing the amorphous layers. For example, a chamber in which the transparent conductive oxide layer (which will be discussed later) can be deposited on the top amorphous alloy layer. be connected to the final deposition chamber.

Since it is clear that it is undesirable that (1) components from the transparent conductive oxide chamber. flowing back or diffusing into the doping chamber, and (2) the substrate material plate in the transparent conductive oxide chamber, the magnetic gas port of the invention is also used, between the transparent conductive oxide chamber and the final deposition chamber. In connection therewith, it is preferable to use the magnetic gas port between all the chambers of the device which are interconnected for the continuous manufacture of amorphous photovoltaic devices.

The invention relates to an improved gas port for substantially reducing the backflow of reactant gas components from one of a pair of adjacent insulated deposition chambers to the other of the pair. The gas port is of the general type, which includes a relatively narrow channel through which. a substrate moves from the first of the adjacent deposition chambers, in which a first layer is deposited on one side of the substrate, to the second of the deposition chambers, in which a second layer is deposited on the first layer. The channel is defined by elongated top and bottom walls and relatively short side walls. The first deposition chamber includes a first conduit through which at least one reactant gas component is introduced into the plasma region and the second deposition chamber also includes a conduit through which conduit 15. at least one additional reactant gas component, which is not introduced into the first deposition chamber, is introduced into the plasma region. The first deposition chamber is further provided with a second conduit at the entrance to the channel for supplying hydrogen, argon or other inert gas to the forward end of the gas port.

20 An evacuation pump works in conjunction with each of the knockdown chambers. The first chamber pump serves to remove substantially all of the at least one reactant gas components that are supplied to the plasma region thereof. The second chamber pump serves to remove substantially all of the at least one additional reactant gas components which are supplied to the plasma region thereof. A second evacuation pump can be positioned at the rear end of the gas port for venting the inert gases.

The gas port is enhanced by the addition of a mechanism intended to extend the non-layered side of a magnetically attractable substrate moving through the channel without making physical contact with the layered side of the substrate. sliding into contact with one of the upper and lower channel walls so that the distance between the upper and lower channel walls can be reduced without the layered substrate surface contacting the other of the upper and lower channel walls. The reduced channel opening results in a reduced backflow of reaction gas constituents from the second deposition chamber to the adjacent first deposition chamber.

8301437 --8-

Preferably, the channel wall in contact with the magnetic substrate is a low friction borosilicate glass sheet with low thermal conductivity. The substrate is made of a magnetic material and is kept in sliding contact with the glass plate by a magnetic field generated by a number of ceramic magnets separated by a number of non-magnetic spacers.

Thus, a first object of the invention is to provide an improved gas port for substantially reducing the backflow of gases from a chamber of a precipitator to an adjacent chamber. The gas port includes a relatively narrow channel through which a substrate moves from the first chamber, in which a first layer is deposited on one side of the substrate, to the second chamber, in which the second layer is deposited on the first layer. The channel is defined by a pair of elongated opposing upper and lower walls and a pair of relatively short opposing side walls. The first chamber includes means for introducing at least one gas to the chamber, the second chamber includes means for supplying at least one additional gas to this chamber and there are members which cooperate with the chambers to discharge the gases from the chambers to feed. The improved gas port is characterized by means around the non-layered side of the substrate, which. moving through the channel. slidably contacts one of the elongated channel walls to reduce the distance between the upper and lower channel walls without the layered substrate surface contacting the other elongated channel wall to allow the backflow of gases from the second room. through_ the gas port channel.

A second object of the invention is to provide an improved gas port, which serves to connect a pair of juxtaposed deposition chambers, said gas port having a relatively small channel, through which a strip of substrate material continuously moving from the first deposition chamber, in which a doped amorphous silicon alloy layer is deposited on one side of the substrate, to the second deposition chamber, in which an intrinsic amorphous silicon alloy layer is deposited on the first layer. The channel is defined by a pair of transparent, elongated, "top and bottom" opposing "top and bottom" walls and a pair of opposing relatively short side walls. The improved gas port is characterized by means intended for generating a magnetic field to slide the non-layered side of a strip of substrate-5 material moving through the channel with one of the elongated walls to reduce the distance between the elongated channel walls without affecting the layered surface of the strip of substrate material moving through the channel contacts the other elongated channel wall.

The invention will be explained in more detail below with reference to the drawing. In the drawing: Fig. 1 shows a partial cross-section of a photovoltaic dentistry fitted with a number of cells of the p-i-n type, each layer of the cells according to the invention consisting of an amorphous semiconductor alloy; FIG. 2 is a schematic of a multi-chamber glow discharge deposition system for continuously manufacturing the photovoltaic devices shown in FIG. 1; FIG. 3 is a partial cross-sectional view of a magnetic gas port showing the arrangement of the ceramic magnets in a cavity in the upper block of the gas port according to the invention, fig. b shows a top view of the gas port according to fig. 3, with dashed lines indicating the separating members, which help to generate the magnetic field, which according to the the invention is advantageously utilized, and FIG. 5 is a schematic representation of a strip of substrate material passing through the gas port channel of the invention and showing the configuration of the upper gas port wall.

30 I. The photovoltaic cell

With reference to the drawing and more particularly Fig. 1 ,. is a photovoltaic cell of the teeth or cascade type, formed from successive pin layers, each comprising an amorphous semiconductor alloy, generally designated 10. It is for the manufacture of this type of photovoltaic device, wherein amorphous deposition layers are continuously deposited on a moving strip of substrate material in successive insulated deposition chambers that the 8301437-10 improved gas ports of the invention have been developed.

More specifically, Figure 1 shows a number of p-i-n type photovoltaic devices, such as solar cells 12a, 12b and 12c. Below the bottom cell 12a is a substrate 11, which can be transparent or consist of a foil with a metal surface. While certain applications may require a thin oxide layer and / or a series of base contacts to supply the amorphous material, the term "substrate" here includes not only a flexible film, but also any elements added thereto by a preceding film. Hormaliter, the substrate material 11 consists of stainless steel, aluminum, tantalum, molybdenum or chromium.

Each of cells 12a, 12b and 12c is made with an amorphous alloy body containing at least one silicon alloy. Each of the alloy bodies includes one. region or layer 20a, 20b and 20c with an n-type guide, an intrinsic area or an intrinsic layer 18a, 18b and 18e, and an area or layer 16a, 16b and 16c with a p-type guide. As indicated, cell 12b is an intermediate cell and, as shown in Figure 1, further intermediate cells can be stacked according to the invention on the cells shown. Furthermore, although pin type tandem cells are shown, the gas ports of the invention are equally suitable for use in a multi-chamber device suitable for manufacturing nip type tandem cells by simply reverse order of deposition of the n-type and p-type layers on the substrate.

For each of cells 12a, 12b and 12c, the p-type layers are characterized by alloy layers that absorb light and have high conductivity. The intrinsic alloy layers are characterized by a set wavelength threshold for solar photoresponse, a high light absorption, a low dark conduction and a large photoconductivity, and these layers comprise sufficient amounts of an energy jump adjusting element or elements for the determined energy jump. make cell application optimal. Preferably, the intrinsic energy jump layers are set such that cell 12a has the least energy jump, cell 12c has the largest energy jump and cell 12b has an energy jump between the other two. The n-type layers are characterized by alloy layers with low light absorption and a high conductivity 8301437 * * - 11. The thickness of the n-type layers can be in the range of about 25 to 100 Angstroms. The thickness of the vessel energy jump for set amorphous intrinsic alloy layers can be between about 2000 and 3000 Angstroms. The thickness of the p-type layers can range from 50 to 200 Angstroms. Due to the small diffusion length of the holes, the p-type layers will generally be as thin as possible. Furthermore, the outer layer, here the n-type layer 20c, will be as thin as possible to avoid absorption of light and need not contain the energy-setting elements.

Obviously, after the deposition of the semiconductor alloy layers, a further precipitation step can be performed in a separate environment or as part of the continuous manufacturing apparatus. At this step, a TC0 (transparent conductive ozyde) -15 layer 22 is added, which layer may consist of, for example, indium tin oxide (ITO), cadmium stannate (Cd ^ SnO ^), or doped tinozyde (SnO ^). Although an electrode grid 2b can be added to the device, for a tandem cell with a sufficiently small surface area, the TCO layer 22 is generally sufficiently conductive so that the grid 2k is not required. If the tandem cell has a sufficiently large surface area or if the conductivity of the TCO layer 22 is insufficient, the grid 2b can be placed on the layer 22 to shorten the carrier web and to increase its conductivity.

II. The Multiple Timing Discharge Precipitators 25 In FIG. 2, a schematic representation of a multiple glow discharge chamber deposition apparatus for continuously manufacturing photovoltaic tandem cells described above is generally illustrated by 26. The apparatus 26 includes a number of isolated assigned deposition chambers, each chamber of the invention being connected to a different chamber by a gas port.

The device 26 is designed to produce a large volume of amophite large area photovoltaic cells having a p-i-n configuration on the deposition surface of a substrate material 11, which is continuously passed through the device from a substrate supply core 11a. to a substrate receiving core 11b. In order to deposit the amorphous alloy layers required to produce a pin configuration, the device 26 includes at least three deposition chambers, each of which includes a first deposition chamber 28 in which an p-type amorphous alloy layer is deposited on the deposition surface of the substrate 11 as the substrate 11 passes through this chamber, a second deposition chamber 30 in which an intrinsic, amorphous alloy layer on the alloy layer of the p-type on the deposition surface of the substrate 11 is deposited when the substrate 11. passes through this chamber, and a third deposition chamber 32 in which an alloy layer with a conductivity of the n-type on the intrinsic layer on the precipitation surface of the substrate r 11 is deposited when the substrate 11 passes through this chamber.

It is understood that (1) although three deposition chambers have been described, further triplets or further individual chambers may be added to the device to allow the device to manufacture photovoltaic cells of any number of amorphous layers; (2) the gas ports according to the invention can also be used in an environment with, for example, two adjacent chambers, in which some tremors or cross-contamination of gases must be prevented between these chambers; (3) Although in the preferred embodiment, the substrate material has been shown and described as a continuous strip of magnetic material, the invention may also be used to deposit successive layers on discrete magnetic substrate plates, which can be continuously monitored by the number of deposition chambers lined; (b) since the length of the path of movement of the substrate through individual deposition chambers is proportional to the thickness of the p-type layer or the intrinsic layer or the n-type layer deposited in a given chamber, the length of the path of movement of the substrate through an individual deposition chamber can be increased or decreased in order to layer with. depositing a desired thickness 30 on the substrate; and (5) although not indicated, other chambers (such as a chamber for adding a TCO layer on the top dopant layer of the photovoltaic device) can be connected to the glow discharge device 26 through the magnetic gas port of the invention.

When the device 26 is used to manufacture p-i-n or n-i-p type photovoltaic tandem cells, further three deposition chambers are connected to the three deposition chambers shown in FIG. In those instances, the device 26 further includes an intermediate chamber (not shown) for circulating the n-type reaction gas mixture flowing through the third precipitation chamber 32 and the p-type reaction gas mixture passing through the first precipitation chamber of the n-type. next three flows, to isolate from each other.

Each of the three deposition chambers 28, 30 and 32 serves to deposit a single, amorphous silicon alloy by glow discharge deposition on the magnetic substrate 11. To this end, each of the deposition chambers 28, 30 and 32 comprises a cathode 3, a, 3, respectively. 3 ^ c, a gas supply line 36a, 36b and 36c, a radio frequency generator 38a, 38b and 38c, respectively, and a number of radiant heating elements Jf0a, ^ 0b and ^ 0c, respectively.

The feed lines 36a-36c are associated with the respective cathodes 3ta-3 ^ c to supply reactant gas mixtures to the plasma regions formed in each deposition chamber 28, 30 and 32 between the cathodes and the substrate 11 moving therealong . Although the feed core 11a. of the magnetic substrate material 11 is shown rotatably arranged in the first deposition chamber 28, and the receiving core-11b of the substrate material is shown rotatably arranged in the third deposition chamber 32, it is understood that the feed core 11a. and the receiving core 11b according to the invention can be arranged in other chambers which are connected to the three chambers shown.

The radio frequency generators 38a - 38c, in combination, operate with the cathodes 3 ^ a - 3 ^ c, the radiant heaters hOa - kOc and the grounded substrate 11 to form the plasma regions in that the elemental reaction gases which are deposited on the deposition chambers 28, 30 and 32 are fed, dies in precipitation species. The precipitate species are then deposited on the substrate 11 as amorphous silicon alloy layers.

To form the photovoltaic cell 10 healed in Figure 1, an amorphous p-type silicon layer is deposited on the substrate 11 in the deposition chamber 28, an intrinsic, amorphous silicon alloy layer on the p-type layer in the precipitation chamber 30 and an n-type amorphous silicon alloy layer deposited on the intrinsic layer in the precipitation chamber 32. As a result, the device 26 deposits at least three amorphous silicon alloy layers on the substrate 11, wherein the intrinsic layer deposited in the deposition chamber 30 differs in composition from the layers deposited in the deposition chambers. 28 and 32 are precipitated by the absence of at least one element, which will be called the dopant or dopant species.

It is essential that the alloy layers deposited on the magnetic substrate 11 be of high purity to produce photovoltaic devices with correspondingly high efficiency. It is therefore necessary to provide means for the in-10. trinsic deposition chamber 30, into which only intrinsic gases for forming the intrinsic alloy layer are supplied, from the dopant deposition chambers 28 and 32, into which the dopant grease gases are introduced. Although the insulation must be sufficient to provide a ratio of at least 10 in the concentration of the intrinsic gases in the deposition chamber 30 to the dopant gases in the dopant deposition chambers 28 and 32, the greater the insulation will be , the furnishings are more efficient.

III. The gaspOften

According to the invention, the required isolation of the intrinsic gases in the intrinsic deposition chamber 30 from the dopant gases in the dopant deposition chambers 28 and 32 is obtained in part by creating a unidiretional flow (in the direction of the arrow hk) from the intrinsic deposition chamber 30 to each of the first deposition chambers 28 and 32. As shown in FIG. 2, the intrinsic deposition chamber 30 communicates with the dopant deposition chambers 28 and 32 through gas ports, shown as slots k2a and kZb which are dimensioned such that the substrate 11 can move through a channel U3 therein as the substrate continuously moves from the feed core 11a, through the deposition chambers 28, 30 and 32 to the take-up core 11b. moves. Heretofore, the dimensions of the gas ports 42a and k2b have been chosen to be as small as possible in order to prevent rearward diffusion or backflow of the dopant gases from the dopant deposition chambers 28 and 32 to the intrinsic deposition chamber 28, while the dimensions at the same time, they were chosen to be large enough to allow the layered substrate surface to pass without passing through the walls of the channel. be scratched. Therefore, the design of the gas ports, 8301437 - 15 - such as 42a and 42b entails a compromise. The channel through the gas ports must be sufficiently large to allow (1) a contact-free passage of the layered surface of the substrate 11 through the ports and (2) a diffusion or backflow of reaction gases from the intrinsic deposition chamber 30 through the ports. prevent. The object of the invention is to reduce the dimensions of the gas port channel to a minimum without scratching the layered substrate surface. It is pointed out again that although the invention mainly relates to preventing contamination of the intrinsic alloy layer by dopant alloy components, the dopant alloy layers can also be protected against security using the magnetic gas port of the invention. to connect the dopant deposition chambers and adjacent chambers, the latter in which, for example, (1) a TCO layer is deposited on the top dopant layer, or (2) the magnetic substrate material is cleaned before entering the deposition chambers. Using the magnetic gas port will also contribute to preventing wafer formation of the substrate in these other chambers.

In order to prevent diffusion of the intrinsic reaction gases from the intrinsic deposition chamber 30 to the dopant deposition chambers 28 and 32 via the gas ports 42a and 42b, the deposition chamber 28 with p-dopant and the deposition chamber 32 with n-dopant at a lower, internal pressurized than the intrinsic deposition chamber 30. To this end, each deposition chamber can be provided with automatic throttle valves, pumps and pressure gauges (not shown). Each throttle valve is connected to a respective deposition chamber and to a respective pump in order to have a surplus of spent precipitation components. remove the precipitation chambers. Each absolute manometer is connected to the respective deposition chamber and a respective throttle valve to control the pressure in the deposition chambers. More specifically, the pressure in the dopant deposition chambers 28 and 32 is preferably kept at a value of approximately 0.55 torr, while the pressure in the intrinsic deposition chamber 30 is preferably kept at a value of approximately 0.6 torr. Therefore, a pressure differential is built and maintained between the dopant deposition chambers 28 and 32 and the intrinsic deposition chamber-30 to provide a substantially unidirectional gas flow through the intrinsic deposition chamber 30.

8301437 - 16 -

In the preferred form of the invention, the intrinsic gases comprise the intrinsic starting materials from which the three deposited amorphous silicon alloy layers are obtained. The intrinsic starting gases may include, for example, silicon tetrafluoride-5 gas (SiP2) plus hydrogen gas, silicon tetrafluoride gas plus silane gas (SiH2), silicon tetrafluoride gas alone or silane gas alone. The intrinsic starting material gases are fed to line 36b and therefore to the intrinsic deposition chamber 30 is fed at a rate which, in conjunction with the rate at which the purge gases are introduced, ensures that (1) the unidirectional flow through the gas ports 42a and tb is present, (2) the intrinsic gases in the dopant deposition chambers 28 and 32 are maintained and (3) substantial backflow or diffusion of the dopant gases in the intrinsic deposition chamber 30 is prevented.

The dopant gasses required to provide the p- or n-type alloy layers in the dopant deposition chambers 28 and 32 are introduced through lines 36a and 36c, respectively. The concentration of the dopant gases required in the precipitation chamber 28 with p-dopant to produce the p-type alloy layer is about 0.1 atomic percent. This dopant gas may be, for example, boron, which is introduced in the form of diborane gas (Bgig). To provide a p-type alloy layer with a higher energy jump, elements such as nitrogen, carbon or oxygen can also be supplied.

The concentration of dopant gasses required in the n-dopant precipitate chamber 32 to obtain the n-type alloy layer is about 0.05 atomic percent. This dopant specialty gas may be, for example, phosphorus, which is used as hydrogen phosphorus gas. or arsenic, which is introduced as arsenic hydrogen gas. In the preferred embodiment, a cleaning gas, such as. . hydrogen, argon or other inert gas is introduced at the forward side (the intrinsic deposition chamber side) of the gas ports tóa and 42b.

The gas enters the intrinsic chamber 30 at the gas ports 42a and 42b through respective lines 37a and 37b, which lines 37a and 37b 35 are provided with openings (not shown) to direct the gas on either side of the magnetic strip of substrate material 11. Due to the pressure difference between the doping chambers 28 and 32 and the intrin 8301437 * s *. IT chamber 30, the inert gases are passed in a unidirectional manner through the channel 43 of the gas ports 42a and 42b. A large percentage of the intrinsic reaction gases, which is fed via the line 36b to the intrinsic chamber 30. is preferably limited to the plasma region of the chamber 30 by introducing and discharging the gases to this region, Similarly, a large percentage of the reactant gas components required for the deposition of the doped layers, supplied to the doping chambers 28 and 32 via respective lines 36a and 36b. The doping gases are also substantially limited to the respective plasma regions of the doping chambers by supplying and discharging these reactant gas mixtures to these regions. gas ports 42a and 42b have been fed to the respective dopant deposition chambers 28 and 32, the inert gases or substantially at the end (the doping chamber) side of the gas ports 42a and 42b are vented, or are vented with the dopant reaction gases. In either case, the cleaning gases serve as an additional measure to substantially prevent backflow or diffusion of dopant gases from the dopant deposition chambers 28 and 32 into the intrinsic deposition chamber 30.

FIG. 3 is an enlarged cross-sectional view of the preferred gas port configuration generally indicated at 42. The gas port 42 of FIG. 3 is intended to be only symbolic of the general arrangement of known components in a typical gas port and does not envisage all known structural elements of this gas port. The description is only fully detailed with regard to the magnetic elements which form the essence of the invention.

More specifically, the gas port ^ 42 generally includes one. lower block 44 and an upper block 46 at the leading edge of which a transverse, elongated, cylindrical roller assembly 48 is attached. The length of the cylindrical roller assembly 48 is preferably at least as wide as the width of the magnetic strip of substrate material 11 passing through the multi-chamber device 26 so that the entire width of the substrate 11 contacts a portion of the substrate. circumference of the cylindrical roller surface. A plurality of roller bearings may be provided for a substantially frictionless rotation of the cylindrical roller assembly 48. The cylindrical roller assembly 48 serves to pass the magnetic strip of substrate material 11 through a relatively narrow gap 8301437-18 or a channel 43. guides formed between the top surface of the lower gas port block 44 and a cut-away portion of the upper gas port block 46. By a unidirectional flow of the inert gas from the intrinsic deposition chamber side of the gas port to the adjacent dopant deposition chambers side of creating the gas port, a significant contamination of the intrinsic down-impact chamber 30 is caused by the back-flow or diffusion of p-type and n-type dopant gases which are fed to the respective adjacent down-impact chamber s 28 and 30 supplied, although the preferred embodiment utilizes a single roller assembly 48 rotatable at h The front end of the gas port 42 may also be attached a second roll assembly rotatably attached to the rear end of the gas port to provide further guidance for the strip of substrate material 11.

The gas port slit or channel 43 has a generally rectangular cross-sectional configuration and is defined by an upper wall 43a, a lower wall 43b and two side walls 43c. As already mentioned, it is desirable that the walls 43c be as short as possible in order to minimize backflow or diffusion of gases through channel 43. In order to achieve this goal, the top wall 43a of the channel. 43 made of. a relatively hard material, which further has the properties of a low frictional surface resistance and a small thermal conductivity. In the preferred embodiment, a backed glass plate 62 of, for example, f, PIREX "(trademark of Corning Glass Works for a borosilicate glass having a softening temperature of 820 ° C, an upper operating temperature during normal operation of 230 ° G and a scleroscope- * * 4 —- U.

hardness of 120) the required properties and is therefore used to manufacture the top channel wall 43a. Although in the preferred embodiment, it is the top wall 43a, which consists of a material with a low frictional surface resistance and a low thermal conductivity (since this is the surface of the top wall 43a, which contacts the non-layered side of the substrate 1.1 ), the bottom wall 43b according to the invention can also be formed in this way (if the layers are deposited on the top surface of the substrate 11). As a further preferred embodiment, the magnetic gas port according to the invention can also be used in. a vertical 8301437-19 oriented cathode array (instead of the horizontal cathode array shown here). According to the invention, with a vertical cathode system, each wall of the gas port can consist of a material with low friction and small thermal conductivity.

In Figs. 3 and 5, the magnetic stripe of the substrate 11 is schematically shown as moving through the channel 43 of a gas port, such as 42. More specifically, Fig. 5 shows the strip of substrate material 11 in sliding contact with the top glass wall 43a of the channel 43. Of particular interest is the small radius 45 of 10 approximately 3 mm, which can be formed at the leading edge of the top glass edge 43a. The radius 45 serves to further prevent the leading edge of the wall 43a from slitting the strip of substrate material 11.

As has already been explained, the channel 43 is partly formed by a cavity 64 in the upper block 46, in which a number of elements are mounted, which serve to bring the substrate 11 into sliding contact with the bottom surface of the glass plate 62. In more detail, an aluminum plate 66 having a thickness of 6 mm and a width of 41 mm and a depth of 19 mm is first placed in the cavity 64; then, in the cavity 64 butting against the aluminum plate 66, a sheath 68 of 304 stainless steel having a width of 40 cm at a depth of 20 cm and a thickness of 3 mm is placed in the cavity 64. finally, a glass plate 62 with a thickness of 6 mm, a width of 40 cm and a depth of 20 cm is placed in the cavity 64, butting against the casing 68. A pair of elongated spacers 25 JQ of 3 mm (1) form the side walls 43c of the channel 43 and (2) determine and fix the depth of the channel opening. It is to be noted that although the preferred height jan is the spacer 3 mm, the height dimension has in practice been reduced to a value of 1.5 mm.

The preferred height dimension of 3 mm represents a very significant reduction in the channel opening since the earlier openings were not smaller than approximately 6 mm. Obviously, as the depth size decreases, the amount of dopant gases that flow back or diffuse through the channel 43 from the dopant deposition chambers 28 and 32 is correspondingly reduced. It has been found that a decrease in the channel opening from the previous dimension of 6 mm to the value of 1.5 mm made possible according to the invention leads to a decrease in impurities, which is 8301437 • 1 Flow back or diffuse from the p-dot precipitate chamber 28 on the n-dopant precipitate chamber 32 to the intrinsic precipitate chamber 30 of at least a factor of 100.

The above discussion shows the importance of the shape of the top wall 43a of the channel 43 from a material which remains essentially planar at the high operating temperatures and temperature variations required for precipitation. The surface of the top wall 43a may inherently warp at fluctuations in temperature: (1) portions of the layered surface of the magnetic substrate 11 would contact the bottom wall 43b of the channel 43 when the substrate passes through it. channel moves, thereby scratching or otherwise damaging one or more amorphous layers deposited thereon, resulting in the efficiency of the photovoltaic device produced therefrom being harmful in a corresponding manner is affected, and (2) the magnetic substrate 11, which is pulled against the top wall 43a, will conform to its surface, which may possibly lead to a wavy or ribbed substrate configuration, on which uneven semiconductor layers would be deposited, thereby also reducing the efficiency of the photovoltaic device. Therefore, a further requirement is characteristic that the material from which the top wall 43a is formed is relatively hard in order to remain substantially planar at high operating temperatures.

In the stainless steel sheath 68, a plurality of magnets, such as 72, are arranged in rows and columns by a number of magnet separators 74 arranged horizontally and vertically. The magnets 72 are preferably ceramic because ceramic materials lead to light and relatively inexpensive magnets, which are stable at high temperatures and generate a strong magnetic field. Although the magnets 72 in the preferred embodiment are shown as long, rectangular ceramic rods 25 mm wide and 50 mm long, the magnets 72 are not limited to ceramic materials or to a particular size or configuration. It is only necessary that the magnets 72 be able to generate a strong magnetic field at the high operating temperatures used for the precipitation. It is preferred that a number of rod magnets be used to generate the total 8301437 4k ^ «

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- 21 «- magnetic .field. This is because the greatest magnetic flux is generated at the ends of the bar magnets T2 and because, therefore, when more magnets are used, the attraction is greater and the magnetic field is more uniform.

The magnetic separators jb consist of substantially flat, elongated, non-magnetic elements, such as aluminum plates with a thickness of 1.5 mm. The dividing plates 74 cooperate with the number of magnets 72 to improve the uniformity of the magnetic field. In the preferred embodiment, total 6b ceramic magnets 72 of 25 mm by 50 mm are separated by non-magnetic separators 74 such that the ends of the circumferential magnets 72 coincide with the edge of the magnetic strip of substrate material 11, . moving through channel 43. Through the magnets 72 with respect to. to provide a magnetic substrate 11, the invention further offers the advantage that the magnetic field is used to center the substrate 11 as the latter moves through the gas port b2. The top block b6 includes a two-piece retaining member 84 (see FIG. 4), which is intended to hold magnets 72 and separators 74 in the preselected pattern.

The top portion of the retaining member 84 interacts with the side portion thereof by a number of screws 86.

Another important advantage is obtained by the magnetic gas port 52 described above. The cylindrical roller assembly 48 is rotatably supported to position the strip of substrate material 11, 25 passing through the channel 43 of the gas port 42 approximately 0.5 mm below the top channel wall 43a. Despite the fact that the substrate 11 is kept under tension, the substrate 11 has the undesirable inherent tendency to bend either transversely or longitudinally of the substrate due to the high operating temperatures to which the latter is exposed. This creates the risk that non-uniform layers are deposited thereon. By generating a magnetic field according to the invention, the strip of substrate material 11 is kept under a greater tension by being pulled up through the magnetic field to contact the top channel wall 43a. This additional stress substantially reduces bending of the strip of substrate material 11 and therefore allows uniform layers to be deposited thereon.

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The top face of the bottom block of the gas port 42 forms. . # the bottom wall 43b 'of the channel 43. In the lower block .tl · there is also a number of bores j6 for receiving elongated heating elements (not shown), the correct number of which depends on the power of each element and the desired temperature at which the substrate 11 is to be maintained as it passes through the channel 43. Both the lower block -44 and the upper block 46 of the gas port 42 have a number of openings JQ in panels 80a and 80b, respectively; which are used to mount the gas port 42 on the deposition chambers. Furthermore, a port 82 provides access to the top block 46 and the aluminum plate 66 to establish communication with the cavity 64. In this manner, the cavity 64 can be cleaned with an inert gas, as discussed above, after the magnetic gas port device is disposed therein, the port 82 being closed by a plug 83 to prevent contamination of the deposition chambers by the ceramic magnets J2.

IV. ' Operation

During operation, the magnetic strip of substrate material 1t becomes voltage from the supply core 11a. directed through: (1) 20 the p-dopant deposition chamber 28, in which a p-alloy layer, such as 16a, is deposited on the underside of the strip; (2) the first gas port 42a; (3) the intrinsic deposition chamber 30, in which an intrinsic alloy layer, such as 18a, is deposited on the p-layer; (4) the second gas port 42b; (5) the n-dopant deposition chamber 32, in which an n-alloy layer, such as 20a, is deposited on the intrinsic layer; and (5) finally being wound onto the take-up core 11b. The gas ports 42a and 42b connect the dopant deposition chambers at the intrinsic deposition chamber 30, while also preventing the backflow or diffusion of reaction gases from the p-dopant deposition chamber 28 and the n-dopant deposition chamber 32 to the intrinsic deposition chamber 30. If further processes, such as applying a T00 layer 22 to the dopant layer 20c, are carried out in further chambers, the latter of which are connected to the three deposition chambers 28, 30 and 32, the improved gas ports 42 according to the invention will also be between these additional chambers and adjacent deposition chambers 35 are applied at (1). contamination of the dopant deposition chambers and (2) reducing the deformation of the magnetic substrate material 11.

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The magnetic field generated by the ceramic magnets 72 according to the invention serves to cover the non-layered side of the magnetic strip of substrate material 11 (made of a material, such as 430 stainless steel), which extends through the channel 43 into the 5 gas port 42 moves to slide into contact with the surface of the top wall 43a. Since the top wall 43a is made of a relatively hard material with low friction and low thermal conductivity, such as a "PHEHEX" (trademark of Corning Glass Work) glass plate, the bottom of the substrate will not be adversely affected. The ceramic magnets 72 generate a uniform magnetic field with very strong forces in a direction perpendicular to the planar surface of the substrate 11 moving through the channel 43, but relatively weak forces in a direction parallel to the planar substrate surface. The magnetic strip of substrate material 11 is therefore simultaneously pulled 1 (1) against the surface of the glass plate 43a, while the strip (2) can slide against it as the strip moves through the channel 43.

The magnets 72, by pressing the magnetic substrate 11 in sliding contact with the specially manufactured top wall 43a of the channel 43, allow a reduction in the width of the channel opening. In other words, special tolerances to prevent scratching of the non-layered sustrate surface become unnecessary, and since the width of the channel opening is reduced, the backflow or diffusion of dopants from the dopant deposition chambers 25 is reduced accordingly, thereby contaminating the intrinsic layer is significantly reduced and a more effective photovoltaic device is obtained. ._ ^ 8301437

Claims (6)

1. Gas port for substantially reducing the backflow of gases from an assigned chamber to an adjacent assigned chamber, where "at the gas port is provided a relatively narrow channel through which a substrate is provided from the first of the adjacent Assigned chambers, in which a first layer is deposited on one side of the substrate, moves to the second of the deposition chambers, in which a second layer is deposited on the first layer, the channel being defined by opposite, elongated upper and lower walls and opposing relatively short walls, the first chamber being provided with means for supplying at least one gas thereto, the second chamber being provided with means for supplying at least one additional gas thereto, and means are present which cooperate with the chambers to exhaust the gases from the chambers characterized by means (72) on the non-layered side of the substrate (11 Moving through the channel (43) into sliding contact with one of the elongated channel walls (43a, 43b) to allow for a reduction in the distance between the upper and lower channel walls, without the layered substrate surface in. contacts the other elongated channel wall to reduce backflow of gases 20 from the second chamber (30) through the gas port channel. Gas port according to claim 1, characterized in that the channel wall (43a, 43b) which contacts the non-layered side of the substrate (11) is made of a material with low friction and low thermal conductivity. Gas port according to claim 2, characterized in that the wall (43a, 43b) contacting the substrate is made of a borosilicate. glass plate exists. , Gas port according to any one of claims 1 to 3, characterized in that the substrate (11) consists of a magnetic material and the substrate 30 is brought into sliding contact with the glass plate (43a, 43b) by magnetic attraction. Gas port according to claim 4, characterized in that the magnetic attraction is obtained by a number of magnets (72). Gas port according to claim 5, characterized in that the magnets 35. (72) are separated by a number of non-magnetic spacers 8301437. characterized in that the allocated adjacent chambers (28, 30, 32) are intended to deposit on the magnetic substrate (11) amorphous alloy layers (16a-16c, 18a-18c, 5 20a-20c). « * 8301437